Such arrangements are best known in automation technology, especially in process automation technology. In such case, field devices are often applied, which serve for registering and/or influencing process variables. Serving for registering process variables are sensors, such as, for example, fill level measuring devices, flow measuring devices, pressure and temperature measuring devices, pH-measuring devices and pH-redox potential measuring devices, conductivity measuring devices, etc., which register the corresponding process variables, fill level, flow, pressure, temperature, pH-value, or conductivity. Serving for influencing process variables are actuators, such as, for example, valves or pumps, via which the flow of a liquid in a pipeline section or the fill level in a container can be changed. In principle, all devices which are applied near to the process and deliver or work with process relevant information are referred to as field devices. Besides the earlier named sensors and actuators, such units, which are participants in a fieldbus system and which are capable of communication with the superordinated units, such as, for example, remote I/Os, gateways, linking devices and radio adapters, are also generally referred to as field devices. A large number of the above mentioned field devices are produced and sold by the Endress+Hauser Group.
In modern industrial plants, field devices are, as a rule, connected, via bus systems, such as Profibus®, FOUNDATION Fieldbus®, HART®, etc., with superordinated units. Normally, the superordinated units are control systems or control units, such as, for example, a PLC (programmable logic controller). The superordinated units serve, among other things, for process control, process visualizing, process monitoring as well as for start-up of the field devices. The measured values registered by the field devices—here especially sensors—are transmitted via the particular bus system to one—or, in given cases, a number of—superordinated unit/units. Along with this, for the purpose of configuring, parametering, or diagnosis of field devices or for the purpose of operating of actuators, data transmission occurs also from the superordinated unit via the bus system to the field devices.
Besides hardwired data transmission between the field devices and the superordinated unit, wireless data transmission, or the radio transmission of data, is becoming always more important. Especially in the bus systems, Profibus®, FOUNDATION Fieldbus® and HART®, wireless data transmission via radio is specified. Additionally, radio or wireless networks for sensors are specified in greater detail in the standard IEEE 802.15.4. For implementing wireless data transmission, newer field devices, especially sensors and actuators, are in part embodied as radio field devices. These have, as a rule, a radio unit and an electrical current source as integral components, wherein, through the electrical current source, an autarkic electrical current supply for the field device is enabled. So-called radio adapters, with which conventional field devices subsequently can be converted into radio field devices, have also become known.